In the packaging of semiconductor chips, the semiconductor chips are often bonded with package substrates. Solders are used to join the bumps in the semiconductor chips to the bond pads in the package substrates. When two semiconductor chips (or one semiconductor chip and a package substrate) are bonded, solder may be pre-formed on one, or both, of the bumps/pads of the semiconductor chips. A re-flow is then performed so that the solder joins the semiconductor chips.